JOURNAL OF COSMETIC SCIENCE 194 artistic blending and shading of hair to produce an overall confi guration on the head containing the originally colored hair fi bers with fi bers of various degrees of lightening. The principal intention of hair bleaching is the destruction of melanin granules by oxida- tion through the action of H2O2 and persulfate salts. Dark brown and Piedmont hair were bleached for 30 min. with a commercial bleaching formulation. For both cases, photographs of virgin and bleached hair are provided in Figure 1. While dark brown hair still contains some pigmentation after the bleaching process, Piedmont hair (yellow hue in the virgin state) becomes very white after treat- ment. Excitation-emission matrices for virgin and bleached dark brown hair are provided in Figure 2. The most apparent difference between the two spectra is the large increase (as a result of bleaching) of the fl uorescence band corresponding to the principal kynurenine peak (Ikyn), which occurs at λex=366 nm, λem=433 nm. There is also a large fl uorescence increase observed at the extreme of the spectrum corresponding to λex=450 nm, λem=509 nm, which we refer to as I509 throughout the text. Trp fl uorescence (ITrp), corresponding to λex=290 nm, λem=343 nm, appears to decrease as a result of bleaching however, this is due to a difference in scale of the two spectra. In fact, Trp fl uorescence increases as a result of bleaching, probably because less melanin is available to absorb light. Figure 1. Photographs of (A) virgin dark brown hair, (B) bleached dark brown hair, (C) virgin Piedmont hair, and (D) bleached Piedmont hair.

2010 TRI/PRINCETON CONFERENCE 195 The corresponding spectra for virgin and bleached Piedmont hair are provided in Figure 3. A numerical summary of these data is provided in Table I. Here, we clearly see an in- crease in Trp fl uorescence as a result of bleaching, both in the case of dark brown and Piedmont hair. We also see a large increase in the fl uorescence of the principal kynurenine peak. The fl uorescence signal of Trp increases only slightly for dark brown hair as com- pared to an almost two-fold increase in Piedmont hair. The principal kynurenine peak, on the other hand, more than doubles for dark brown hair and increases by one-half for Pied- mont hair. The peak intensity at the extreme of the spectra remains the same for Pied- mont hair. It is interesting to examine the changes in the ratio of ITrp/IKyn and I509/ IKyn. Bleaching results in a decrease in ITrp/IKyn for dark brown hair and an increase in this same ratio for Piedmont hair. Curiously, the ratio of the peak at the longest excitation Figure 2. Excitation-emission matrices of (A) virgin and (B) bleached dark brown hair.